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  • Chemistry  (260)
  • Ultrastructure  (3)
  • Magnetism
  • 2000-2004  (2)
  • 1975-1979  (48)
  • 1960-1964  (124)
  • 1950-1954  (89)
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Year
  • 11
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 26 (1954), S. 94-96 
    ISSN: 0009-286X
    Keywords: Chemistry ; Industrial Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Die konstruktiven Voraussetzungen für Laboratoriumszentrifugen mit bisher in der Praxis nicht erreichbaren Fliehkräften werden dargelegt. Das entwickelte Gerät, das im Gegensatz zu anderen Bauarten nur eine einzige radial um die Drehachse rotierende Zelle für die Einsatzflüssigkeit besitzt, wird beschrieben. Es ermöglicht bei 84 000 U/min Normalbeschleunigungen von 584 000 g, bei 120 000 U/min und kleineren Präparatmengen von 915 000 g. Besondere Einsätze zur Erfassung des Sediments bringen bei präparativen und möglicherweise auch analytischen Arbeiten besondere Vorteile.
    Additional Material: 3 Ill.
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  • 12
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Organic radicals were produced in the tensides C16H33(OCH2CH2)21OH and C14H29(OCH2CH2)3-SO3Na in aqueous solutions using a short pulse of high energy electrons. The radicals were formed by OH attack on the (OCH2CH2)x-parts of the tensides. The decay of the 250nm absorption of the radicals was recorded at different initial radical concentrations and tenside concentrations. Several radicals could be produced in one micelle. Radicals formed in the same micelle decay within microseconds or faster. The half life time τ1 in a micelle carrying two radicals is 2,0·10-6 s for C16H33(OCH2CH2)21 OH and less than 6·10-7 s for C14H29(OCH2CH2)3SO3Na. A model for intramicellar radical-radical reactions is proposed according to which the rate is faster in tensides of high critical micelle concentration. Single radicals in micelles of C16H33(OCH2CH2)21OH can deactivate each other without leaving the micelles. This intermicellar reaction is discussed in terms of the rate of diffusion-controlled micelle-micelle encounters, an encounter time of 7·10-8s, and the above time τ1 for intramicellar reaction. The observed rate constant 2k of intermicellar reaction is 3,5·106 mol-1·l·s-1. At low tenside concentrations, the bimolecular rate constant increases since more single tenside radicals are present in solution. They react rapidly (ca. 108 mol-1·l·s-1) with radicals in micelles. Single radicals in C14H33(OCH2CH2)3-SO3Na micelles cannot directly react with each other because of the Coulombic repulsion between two anionic micelles. Reaction occurs after the exit of a tenside radical from its micelle, the rate of which depends on the micellar equilibrium Mn⇄Mn-1+M (M: tenside molecule; n: agglomeration number of micelle). A single radical in solution reacts with a single radical in a micelle with 2k = 1,0·108 mol-1·l·s-1 and with another single radical in solution with 4,0·107 mol-1·l·s-1.γ-Irradiation of both tensides in aqueous solution leads to slight increases in viscosity, followed by turbidity beyond the “gel dose” and phase separation. These effects are explained in terms of crosslinking of tenside molecules. Formation of a large network requires bridges between all participating tenside molecules (not only bridges between micelles).
    Additional Material: 11 Ill.
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  • 13
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Es wird die Spaltung der Mutterkornalkaloide vom Polypetid-Typus mit Hydrazin beschrieben. Neben kleineren Spaltstücken wird die vollständige Peptidseitenkette als dreigliedriges saures Spaltstück erhalten, wobei das bei der totalen Hydrolyse mit Säuren und Alkalien als Ketosäure auftretende Glied nun in reduzierter Form erhalten wird. Aus Dihydro-ergotamin isolierte man Propionyl-L-phenyl-alanyl-L-prolin und aus den anderen Alkaloiden die entsprechend aufgebauten Peptidsäuren, deren Konstitution durch Synthese bewiesen werden konnte.
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  • 14
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 33 (1950), S. 108-116 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Als Modellversuche für die Partialsynthese der natürlichen Mutterkornalkaloide vom Peptidtypus und zum Studium des Zusammenhanges zwischen Struktur der Peptidseitenkette und pharmakologischer Wirkung wurde eine grössere Anzahl von Peptiden der isomeren Lysergsäuren und Dihydro-lysergsäuren hergestellt, analysiert und charakterisiert.
    Additional Material: 4 Tab.
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  • 15
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 33 (1950), S. 343-349 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Le viburnitol extrait de Viburnum tinus L. est identique au l-quercitol de Gymnema sylvestre Br. A l'état dûment purifié il ne peut remplacer le méso-inositol comme facteur de croissance pour Eremothecium Ashbyii et pour le mutant “inositolless” de Neurospora crassa. Les composés phospho-organiques acido-solubles des fruits de Viburnum tinus consistent essentiellement en esters inosito-phosphoriques.
    Additional Material: 2 Ill.
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  • 16
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 33 (1950), S. 1751-1770 
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Aus den Knollen von Eleutherine bulbosa wurde ein bisher unbekanntes, rechtsdrehendes Naphtochinon, Eleutherin (I), isoliert und in seiner Konstitution aufgeklärt. I enthält einen Dimethylisopyranring; es konnte unter Ringöffnung über das furanoide Reduktionsprodukt XVIII in das gelbe, optisch inaktive ψ-Eleutherin (XXIII) umgewandelt werden.
    Additional Material: 3 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 1 (1978), S. 97-97 
    ISSN: 0935-6304
    Keywords: Liquid Chromatography ; Structure and relation of polyhalogenated aromatics ; discussed ; Silica gel/aluminium oxide compared ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
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  • 18
    ISSN: 0935-6304
    Keywords: Gas chromatography ; Capillary, glass ; Separation of polychloro biphenyls ; Separation of organochlorine pesticides ; Splitless automated injection ; Residue level ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Complicated PCB mixtures can be separated in individual compounds using glass capillary gas chromatography, (GC)2. Depending on extraction and clean-up procedure it is also possible to separate and determine organochlorine pesticides at the same time.This (GC)2 technique can be used to determine the contents of individual chlorinated biphenyls in milk products and animal feedstuffs and in the analysis of complicated extracts of soil and vegetable material.Practical aspects concerning connection of the capillary, automatic splitless injection, repeatability of the retention time, quality of the column with respect to separation and adsorption and degradation of DDT are discussed.The detection of individual chlorinated biphenyls is possible at the ppb level in fats and vegetable materials, using an extraction and clean-up procedure, based on saponification of the sample.Preliminary results for milk, obtained from several areas, are shown.
    Additional Material: 6 Ill.
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  • 19
    ISSN: 0935-6304
    Keywords: Comprehensive two-dimensional gas chromatography ; thermal desorption modulator ; temperature programming ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: ---In comprehensive two-dimensional gas chromatography, two individual separations are coupled by means of a rotating thermal desorption modulator interface. The injection pulse introduced via the interface onto the second column should be as short as possible. Parameters affecting the modulator operation are studied. In the set-up used in this study, the temperature of the second column can be programmed independently from that of the first column. Optimization of the second-dimension separation to minimize peak broadening and maximize resolution is discussed and an elegant approach to determine second-dimension retention times using a non-constant modulation frequency is demonstrated. The high separation power of the comprehensive system is demonstrated by the analysis of technical and biota samples containing chlorinated biphenyls and toxaphene.
    Additional Material: 7 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 5 (1954), S. 172-177 
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: The application of Electro-chemical Methods to the Investigation of Corrosion of Steel by FluoridesElectro-chemical methods can be advantageously employed in investigations on the corrosion of steel by Fluorine compounds and Hexafluosilicic acid compounds, such as are frequently to be found in mixtures used for the preservation of wood. Evidence of passivation by covering can be recognised by the anodic leg of the current potential curves obtained when steel is immersed in various solution containing alkaline fluorides. These are distinctly noticeable in the case of solutions containing alkaline fluorides, but the effect is not quite so marked with solutions containing Bifluorides. The low solubility of the products of corrosion and higher concentrations of solutions, with resultant formation of covering layers, favour the appearance of these effects. However, passivity cannot be substantiated in the case of solutions of hexafluosilicic acid and its salts. The anodic behaviour of steel in the various solutions under notice in this article runs on parallel lines with that which results from continuous immersion of steel in similar solutions.
    Notes: Zur Klärung der bei Korrosionsuntersuchungen an Stahl in Lösungen von Fluorverbindungen und Hexafluorkieselsäureverbindungen, wie sie häufig im Gemisch für Zwecke des Holzschutzes verwendet werden, können elektrochemische Methoden mit Vorteil angewandt werden. An den anodischen Ästen der Strom-Spannungskurven von Stahl in den verschiedenen fluoridhaltigen Lösungen können Passivitätserscheinungen durch Bedeckung erkannt werden. Diese sind in den Lösungen der Alkalifluoride besonders deutlich, in den Bifluoridlösungen ebenfalls, aber nicht so ausgeprägt vorhanden. Die gering Löslichkeit der entstehenden Korrosionen begünstigen infolge Deckschichtenbildung; dagegen ist in den Lösungen der Hexafluorkieselsäure und deren Salzen eine Passivität nicht festzustellen. Das anodische Verhalten von Stahl in den verschiedenen Lösungen, das in Korrosionsstromversuchen verfolgt wird, läuft parallel mit den Befunden von Dauertauchversuchen in den entsprechenden Lösungen.
    Additional Material: 9 Ill.
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